In recent years, a wireless communication system which connects a plurality of communication devices through short-range wireless communication is increasingly used. As an example of using short-range wireless communication, an activity recording system including, as two communication devices, a sensor device for measuring a physical quantity, and a data storage terminal for storing data received from the sensor device, is developing. For example, in JP-A-2013-233342, an activity meter capable of performing short-range wireless communication is a sensor device, and a terminal such as a smart phone, etc. is a data storage terminal, and short-range wireless communication is performed therebetween. Accordingly, the activity meter and the smart phone are synchronized with each other, and an activity amount measured at the activity meter is stored in the smart phone.